1. Field of the Invention
The invention relates generally to a memory management mechanism of a multiprocessor system and, more particularly, to applying a virtual memory scheme to a direct memory access (DMA) mechanism.
2. Description of the Related Art
A common technique in computer systems is to provide one large virtual address space, which divides a physical memory into smaller blocks called segments and pages. These smaller blocks can then be allocated to different processes. In a conventional symmetric multiprocessor (SMP) system, multiple processors have access to this common shared virtual address space and physical memory. Each processor has a memory management unit (MMU), which translates processor instruction and data addresses to physical memory addresses.
Typically, a non-homogeneous multiprocessor system has one or more general-purpose processors such as processing units (PUs) on the one hand and one or more special-purpose processors such as synergistic processor units (SPUs) on the other hand. Such a non-homogenous multiprocessor system also has a system memory. The general-purpose processors generally use virtual addresses to access and manage the system memory. Typically, a memory management unit (MMU) coupled to a general-purpose processor takes care of accessing and managing the system memory by means of the virtual addresses. By contrast, special-purpose processors generally adopt a direct memory access (DMA) mechanism, which utilizes only physical addresses. Thus, the different types of processors cannot access the same object stored in the system memory with the same virtual address. This leads to difficulty in building a cooperative programming model between programs running in those different types of processors.
In some cases, SMP systems may have one or more processors having a DMA mechanism on the one hand and one or more processors using a virtual memory system on the other hand. In such cases, the processors having the DMA mechanism use only the physical addresses of their memory hierarchy. Hence, the similar problem and/or difficulty as mentioned above in relation to the non-homogeneous multiprocessor system.
Therefore, a need exists for a system and a method for improving memory management in a multiprocessor system.